1. Field of the Invention
The invention relates to fruit food processing and products produced therefrom. More specifically, the invention relates to a process of producing high fruit content ready-to-eat foods through form shaping.
2. Description of Related Art
Since Adam and Eve, fruit has been universally recognized as a highly desirable food. Further, the need for consuming significant quantities of fruit for nutritional purposes is well documented. One reason the public does not consume the recommended quantities of fresh fruit is spoilage; fruit is highly perishable. Thus, the fruit is typically processed to extend its life by canning, freezing or by various evaporative approaches such as sun drying (raisins), hot air drying (dried fruit), freeze drying (blueberries for dry cereal), frying (sliced bananas), spray drying (fruit powders) and dehydration to very low moistures (for dry cereals).
Each of these processes has its strengths and weaknesses. Sun drying in the desert works well in California apricots, but not in Washington apples, Michigan cherries, or Florida tomatoes. Hot-air drying makes soft fruit lacking the crispness of fresh fruit and can yield to mold and yeast spoilage over time. Freeze drying is an elegant way to dry fruit, but it is very expensive (an order of magnitude greater than fresh fruit weight-for-weight), limiting it to high-margin products or small percentages in foods. Frying imparts fat, offsetting the nutritional value and flavor of fruit. Spray drying of fruit, limited mostly to pulp-free juices, requires a carrier, such as maltodextrin, that limits the fruit content. Dehydration to moisture less than 3% depletes volatile flavors and makes a crispy but hygroscopic fruit that rapidly absorbs humidity and can become tough and hard.
Although it would be desirable to form edible high fruit content foods, the potential for providing such fruit foods is limited by the processing difficulties associated with fruit compared to other food foods. For example, extrusion technology is employed extensively throughout the grain processing industry (but not in fruit processing) to cook grain-based and soy foods because the process is energy efficient, reliable, and sanitary. Major industry segments utilizing extrusion cooking include ready-to-eat cereals, snacks, pet foods, industrial pre-gelled flours, and many others.
Starches, flours, and meals milled from grain have traditionally been used by those skilled in the art of extrusion to manipulate texture and density of cereal foods, such as ready-to-eat breakfast cereals; snacks, such as corn puffs and onion rings; pet foods, such as kibbled dog foods; and many other foods. Starches are long-chain carbohydrates that, when gelatinized by extrusion cooking, form films capable of trapping gas (air and steam) in thin-walled, honey-comb-like structures, aerating the product (“puffing”), and reducing the density.
Some limited attempts to use extrusion technology for fruit have met with mixed results. Typically, the fruit content is severely limited, and in some cases eliminated, so that the technology is virtually identical to the extrusion cooking of grain without fruit. In such cases, the principal ingredients are flours, starches, sugars, gels, gums, flavors and colors, with a small percent of dried or powdered fruit. Fruit powders have been added in low percentages such as in some popular breakfast cereals to impart fruit flavor, color, or marketing sizzle to starch-based puffed foods.
Extrusion technology uses a cooking extruder. A cooking extruder is typically a screw machine that accepts free-flowing grain meal or flour as in-feed material into a progressively reducing, spiral-screw cavity. As the material progresses along the screw or multiple screws of the extruder, the in-feed material is hydrated by water injection (for example, from a 10-12% in-feed moisture to a 15-30% dough moisture), and the moistened material is compressed and heated by friction to “pressure cook” the extrusion dough with the moisture encapsulated as steam. Typically, extrusion in-feed materials must be uniformly free flowing and finely granular, both hallmarks of milled grains such as corn meal, wheat and rice flours, etc. By contrast, fruit foods (i) are not as free flowing, causing stoppage of the in-feed material (except in forms too liquid for extrusion cooking), (ii) are often heterogeneous in particle size or granulation, and (iii) are hygroscopic when dried. These characteristics during the 55-year history of food extrusion processing have virtually eliminated extrusion cooking from consideration when processing fruit.
Baking, another commonly used process for forming a product, also has difficulties producing a high fruit content product. As background, baking is a process in which grain-based carbohydrates (typically ground flours or meals derived from wheat, corn, rice, etc.) are admixed with various other functional ingredients (liquids such as water or milk, flavorings such as sugars or salt, texture elements such as fats, leavening agents such as yeast or sodium bicarbonate, etc.) to form a batter or dough, then heated (hot air, hot oil, hot solid surface, direct flame, etc.) to create digestible foods. Ungelatinized (uncooked) flours are poorly digested in the stomach, and can create gastrointestinal and nutritional dysfunctions if consumed raw. Baking is a process that simultaneously cooks the grain-based ingredients (i.e., gelatinizes the starches) and dries the food into a soft, chewy or hard (crispy, crunchy, etc.) food form. Generally baking transforms a raw food, composed of ungelatinized starches, unprecipitated proteins, inactive leavens, etc., from a thick batter or dough form into a drier embodiment that can be readily handled (e.g. a finger food), sliced (e.g., breads, cakes) or broken by hand into edible portions.
For example, in the 19th century, Sylvester Graham promoted a form of whole wheat flour that included the wheat germ. Later in the century, his flour was sweetened with honey, etc. and baked into Graham crackers. In modern times, homemakers have sought easier techniques to create edible pie crusts that did not require the steps of measuring multiple ingredients, skillfully cutting in cold shortening into the dough, rolling and layering the cold dough, and handling of fragile rolled dough to form the pie crust. Consequently, coarsely crushed graham crackers, sugar and melted butter have become popular pie shells for flavor and texture reasons, and especially for their ease of pie crust formation in the kitchen. The tacky mixture is simply pressed by hand into a pie plate, and then baked at 375 degrees F. for 10 minutes to “set” the crust. Graham cracker pie shells formed in food processing plants by this process are ubiquitously available in grocery stores. In the simple graham cracker crust recipe, each ingredient serves multiple functions. The graham cracker crumb, comprising most of the crust recipe, is the pregelatinized carbohydrate source (substitute for raw flour) contributing flavor, texture, and structure to the molded crust. The butter, composed of approximately 82% butterfat and 15-18% water, is respectively the texturizing (fat) component and the liquid (solublizing) component that makes the granular mixture tacky. The granular sugar becomes dissolved in the moisture as the baking temperature rises; then it recrystalizes into a structural, glue-like element of the crust after baking desiccates the crust. Upon cooling, the butterfat congeals to further strengthen the crust structure. Thus the baking of the pressed, tacky granular mixture at 375 degrees for 10 minutes is a traditional use of baking to dry the crust for structural and crisping reasons.
Such a baking process would be difficult to produce a high fruit content product with crispy or crunchy characteristics or other characteristics, because the baking process uses a pregelatinized carbohydrate source not found in fruits. Further, the heat commonly associated with baking temperatures may adversely affect the nutritional value and other aspects of a high fruit content product. A different process for forming high fruit content products is needed.
Another process for molding three-dimensional shapes of a granular starch-based food was developed in Belgium in the late 19th century. Sugar cubes are made by moistening granular sugar to approximately 1% water content, then pressing the tacky granular mixture at room temperature to form a cube, then desiccating the cubes with heat lamps to “set” the structure of the sugar cube without melting the sugar. The Applicant understands that in this process, the starting material, pure crystalline sucrose with 0% water, is wetted to approximately 1% water to create a slightly tacky mixture, which is then added loosely into a mold and cold-pressed in the form to create a cube shape. The sucrose crystals contain a high level of moisture on the outside of each crystal, while the inside of the crystal remains essentially at 0% moisture. The moisture on the outside of the crystal allows a limited degree of sugar “melting” (depending on the amount of water added) that with desiccation will become the “glue” that will anneal the crystals together into the cube shape. After formation of the cube, the room temperature shapes are extracted immediately, then heat is applied to the formed piece to desiccate it as soon as possible back toward 0% water. The purpose of the heat is to remove all the added water, a step analogous to the desiccation function of baking. However, since the heating process desiccates from the outside in, the core of the cube retains a relatively higher moisture level that must equilibrate in a “conditioning” step that occurs over a day or so prior to packaging. The restored molecular crystalline structure resists moisture pick up under ordinary dry storage conditions, allowing packaging in porous containers, such as paper.
Known processing techniques for raw fruit have also not resulted in a satisfactory high fruit content food that can meet the needs of consumers. Extrusion principles, baking, and moistening processes that are used for starch-based products traditionally have not resulted in a satisfactory high fruit based food. Thus, there remains a need for a process that can form a high fruit content food with desirable characteristics.